Not vernal
The Not vernal , (noted γ or G ), is one of the two points of the celestial Sphère where the celestial equator and the ecliptic cross. Precisely, this point is defined by the position of the Sun on the celestial sphere at the time of the equinox of March (spring in the northern hemisphere).
In Astronomy, the Méridien of the vernal point is used as reference in the equatorial Frame of reference, it is defined like meridian line zero for the measurement of the right ascensions. The right ascension of the vernal point is thus α = 0:00 .
Being located on the celestial equator, the variation of the vernal point is by δ definition = 0 °.
In Astrologie this point bears the name of “first point of the Ram”, according to the name of the Constellation in which it was in the Antiquité. However, because of the Precession of the equinoxes, this point moves slowly along the ecliptic. The vernal point is currently located in the Constellation of the Poisson, it entered there towards -60 and will come out from it towards 2600 to enter the constellation of the Verseau.
Determination of the vernal point
The vernal point being defined like the crossing of the ecliptic and the celestial equator, it changes position with the movements of Précession and Nutation of the axis of rotation of the Ground. These parameters are determined by the International Earth Rotation and Reference Systems Service (IERS) by combining the abundant data by a world inspection network. Because of the movements of the vernal point, these are the coordinates J2000.0, i.e. at January 1st 2000 at midday UTC, which are used as reference for the equatorial frame of reference.
See too
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